Method of identification of living body and apparatus for identification of living body

ABSTRACT

A method of identification of a living body is provided. The method comprises steps of detecting an electromagnetic wave in a frequency band ranging from 300 GHz to 30 THz transmitted from the living body, extracting plural kinds of information from the detected electromagnetic wave, and deriving therefrom information on the living body and information inherent to the living body, and comparing the information on the living body and the information inherent to the living body with preliminarily memorized information. This method identifies an individual living body with improved real-time detectableness and higher security to prevent illegal pretension.

TECHNICAL FIELD

The present invention relates to a method of identification of a livingbody by utilizing biological information of the living body, and anapparatus therefor.

BACKGROUND ART

Investigations are being made on identification of living bodiesincluding individual persons. Some methods and apparatuses foridentification of an individual person conduct the identification byutilizing a physical feature of the individual person such as afingerprint, a voiceprint, a voice, and a retina. Such an identificationapparatus, which utilizes only a characteristic pattern of the specifiedfeature of the person, has problems in security, since another personcan obtain and imitate the pattern data. Actually, a second person cansimply cut out the physical characteristic portion from a first personand can pretend to be the first person.

To cancel the above disadvantage, methods and apparatuses foridentification of the individual person have been disclosed as shownbelow.

Japanese Patent Application Laid-Open No. 2001-195364 disclosescombination of two or more identification systems such as retinaidentification, fingerprint identification, voice identification, andvoiceprint identification to improve real-time responsiveness (quickidentification of the objective person to be true) for security.

Japanese Patent Application Laid-Open No. 2002-236666 employs additionalsystem for checking the quality of the biological information such as afingerprint, a voiceprint, a face feature, and an iris to improvereal-time detectableness in the identification for security. Theinformation-quality-checking system is exemplified by a temperaturesensor, a skin electroconductivity tester, and an image pickup apparatusfor observation of movement of a mouth or an iris.

The method of using plural kinds of individual identification systems,like the method disclose in the above Japanese Patent applicationLaid-Open No. 2001-195364, requires combination of many individualidentification systems for real-time individual identification. However,use of the plural identification systems necessarily makes larger thesystem constitution of the identification apparatus disadvantageously.Further, the use of the plural systems for individual identification canbe ineffective if a second person imitates all the objective physicaldata of the individual identification apparatus. Thus, even if thismethod can increase the probability for the precise identification of anindividual person, it is difficult to prevent completely the falsepretension.

The method of additional use of an information-quality-checking systemfor securing the real-time responsiveness of the individualidentification system, like the method of above Japanese PatentApplication Laid-Open No. 2002-236666 can improve greatly the real-timeresponsiveness. However, the system is necessarily larger correspondingto the information-quality-checking system, disadvantageously.

Any of the above disclosures improves the real-time responsiveness toprevent pretension to be the subject person for higher security.However, for the real-time responsiveness, plural identification systemsshould be employed, or an information-checking system should be added,which enlarges the entire identification system. In particular, inrecent years, mobile products such as a mobile phone have come to bewidely used. The individual identification apparatus for reservationsystems, cashing systems, and the like employing the mobile product arenaturally demanded to be smaller in size.

DISCLOSURE OF THE INVENTION

For solving the above problems, the present invention provides a methodof individual person identification and an apparatus thereforconstituted as shown below.

According to an aspect of the present invention, there is provided amethod of identification of a living body, comprising the steps of:

detecting an electromagnetic wave in a frequency band ranging from 300GHz to 30 THz transmitted from the living body;

extracting plural kinds of information from the detected electromagneticwave derive therefrom information on the living body and informationinherent to the living body; and

comparing the information on the living body and the informationinherent to the living body with preliminarily memorized information.

The information on a living body is preferably any one selected from thegroup consisting of information on movement of the living body andinformation on a property of a material comprised of the living body.

The information on movement of the living body is preferably any oneselected from the group consisting of pulse vibration, voice cordvariation, bone vibration, shape change of eye lens, pupil contractionand pupil dilation.

The information on a property of a material comprised of the living bodyis preferably any one selected from the group consisting of atemperature of the living body, absorption of the electromagnetic waveby the living body, reflection of the electromagnetic wave by the livingbody, an impedance of the living tissue, a dielectric constant of atissue of the living body, DNA, and a water content of a tissue of theliving body.

The information inherent to the living body is preferably any oneselected from the group consisting of a fingerprint, a voiceprint and aretina pattern.

The step of detecting an electromagnetic wave is preferably comprised ofthe step of projecting an electromagnetic pulse wave to the living bodyto detect a reflected wave of the electromagnetic wave.

According to another aspect of the present invention, there is providedan apparatus for identifying a living body, comprising:

a detecting section for detecting an electromagnetic wave in a frequencyband ranging from 300 GHz to 30 THz transmitted from the living body;

an information-collecting section for extracting plural kinds ofinformation from the detected electromagnetic wave to derive therefrominformation on the living body and information inherent to the livingbody; and

an identifying section for comparing the information on the living bodyand the information inherent to the living body with preliminarilymemorized information to identify the living body.

According to the present invention, from electric wave transmitted froma living body, plural kinds of information are derived, and theindividual person is identified by combination of the plural kinds ofinformation. Thereby plural systems need not be employed for detectionof the information of the living body, which simplifies theidentification apparatus constitution effectively.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a drawing for explaining the constitution of theidentification apparatus of the present invention.

FIGS. 2A and 2B are drawings for explaining the voiceprintidentification apparatus of Example 1.

FIGS. 3A, 3B, 3C, 3D and 3E are drawings for explaining the operation inExample 1.

FIG. 4 is a drawing for explaining the fingerprint identificationapparatus of Example 2.

FIGS. 5A, 5B, 5C, and 5D are drawings for explaining the operation inExample 2.

FIG. 6 is a drawing for explaining the retina identification apparatusof Example 3.

FIGS. 7A, 7B and 7C are drawings for explaining the operation in Example3.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention are explained below by reference todrawings. In the description, the reference symbols are the same as theones in the drawings.

FIG. 1 is a block diagram of the identification apparatus of the presentinvention. The identification apparatus of the present invention isconstituted of electromagnetic wave-detecting section 101, biologicalinformation-collecting section 102, biological information-memorizingsection 103, and identifying section 104:

the electromagnetic wave-detecting section 101 detects electromagneticwave transmitted from a living body;

the biological information-collecting section 102 extracts plural kindsof information from the electromagnetic signals detected byelectromagnetic wave-detecting section 101, and collects information onthe living body and information inherent to the living body from theextracted plural kinds of information;the biological information-memorizing section 103 memorizes referenceinformation necessary for identification of the living body from theinformation (information of the living body and information inherent tothe living body) collected by biological information-collecting section102; and the identifying section 104 compares the respective kinds ofinformation collected by the biological information collecting sectionwith the reference information memorized in biologicalinformation-memorizing section 103, thereby judges whether or not theliving body is the objective living body, and outputs (107) the judgmentresult as the identification result.

In the present invention, an electromagnetic wave is employed as themeans for sensing the biological information. This electromagnetic waveis a pulsed or continuous electromagnetic wave of any frequency in afrequency range from 300 GHz to 30 THz (hereinafter referred to as a“terahertz wave”). The terahertz wave has properties of theelectromagnetic wave: rectilinear propagation and some penetrativenessthrough an article. Such properties are applicable widely in varioustechnical fields: measurement of a position of an article through anobstacle (an inorganic material) with accuracy of an order of tens ofmicrometers from phase delay by an obstruction like a radar; imageformation by utilizing spectral information or absorption/reflectionproperties; and like application fields.

By an analogous technique, an article can be sensed through anobstruction by a millimeter wave. However, with this technique, thearticle cannot be identified through the obstruction even though thepresence of the article can be detected, since the millimeter wavecannot be focused sharply owing to the long wavelength of thiselectromagnetic wave in comparison with the terahertz wave. For example,in detection of a human body caught under tiles and rocks, themillimeter wave can detect the presence of a thing like a living bodydifferent from the tiles and rocks, but cannot obtain the informationwhether the living body is human body, whether the living body isbreathing, or in what state the living body is buried.

The frequency region of the terahertz covers absorption wavelengths ofmany biological molecules of proteins or the like. Therefore theterahertz wave can be useful characteristically in various applicationfields such as sensing of a non-labeled biological molecule, and imagingof a biological molecule by difference in a propagation state of theterahertz wave. In the above-mentioned example of detection of a humanbody under the tiles and rocks, sensing of the biological molecules maygive information on the name of the person or the health state of theperson, not only the state of the human body. Therefore the techniqueemploying the terahertz is obviously different from the techniqueemploying the millimeter wave.

Generally an article is known to radiate an electromagnetic wavedepending on the temperature T thereof according to the Planck'sequation below.

${{Bv}(T)} = \frac{\frac{2{hv}^{3}}{c^{2}}}{{\exp\left( \frac{hv}{kT} \right)} - 1}$where B_(ν)(T): spectral radiance; h: Planck constant, ν: frequency; c:light velocity; k: Boltzmann constant, T: absolute temperature of anarticle. Therefore, a passive type system can be constituted withmeasurement of electromagnetic spectra depending on the absolutetemperature an article.

Electromagnetic wave-detecting section 101 is constituted of a part forgenerating/irradiating a pulsed or continuous terahertz wave and a partfor detecting a terahertz wave containing superposed biologicalinformation. The terahertz wave-generating/irradiating part may be afrequency conversion system which converts ultrashort pulse signals intoa pulse wave within the aforementioned electromagnetic frequency bandwidth by a light transmission element or the like. However, in theindividual person-identifying apparatus of the present invention, theterahertz wave-generating/irradiating part is not limited theretoprovided the part is capable of generating the above-mentioned terahertzwave in a pulse shape or a continuous wave shape. The terahertzwave-generating/irradiating part may be constituted to vary thedirectivity of the terahertz wave to conduct sensing in an intendedrange. In this constitution, the sensing mechanism may be a mechanicalconstitution with an actuator, or may be a constitution in which anantenna is provided in the terahertz generating/irradiating part and thedirectivity of the antenna is made variable, but the constitution is notlimited thereto, insofar as the part is capable of sensing a living bodywith the terahertz wave. The other part of the electromagneticwave-detecting section, namely a terahertz wave-detecting part fordetecting a terahertz wave containing superposed biological information,may be a system employing a light transmission element, or a systememploying an electromagnetic wave detecting element like a bolometer,but is not limited thereto. Besides the constitution which projects aterahertz wave to a living body and detects a change of the terahertzwave transmission state by the reflected wave as described above, theelectromagnetic wave-detecting section 101 may have a constitution inwhich a terahertz wave emitted from a living body is detected, orterahertz-generating element is provided in the living body side and theterahertz wave from the element is detected.

Biological information-collecting section 102 collects plural kinds ofbiological information detected by electromagnetic wave-detectingsection 101 (information on the living body and information inherent tothe living body) for identification by isolation and extraction from theterahertz wave carrying the information in superposition.

In the present invention, the information extracted from theelectromagnetic wave transmitted from a living body includes a phasechange. The phase change can be used for detection of positioninformation showing movement of the living body. For example, forobtaining human voice information, phase information is firstlycollected from electromagnetic wave information inputted to biologicalinformation-collecting section 102 by a phase detecting circuit, andfrequency of the voice is detected from the periodicity of the phaseinformation. Then a signal in the voice signal frequency band isextracted by use of a filter or the like to obtain biologicalinformation of bone vibration caused by voice sound transmitting througha human body. Otherwise information on biological information such asbreathing and pulse can be obtained by extracting a relatively regularvibration component such as a vertical movement of a breast, and avibration component of a skin surface. Besides the inherent vibration ofthe human body, movement of a muscle or bone joint of a human body canbe extracted by detecting a terahertz wave at a fixed detection site (afixed point or a region on a human body) and plotting the phasedisplacement at the detection site in time series. Other than thebiological information on the movement of living body, informationinherent to a living body (a pattern inherent to the living body) can beobtained by sensing a part of the living body (specifically a humanbody). For example, a voiceprint or a fingerprint can be collected asthe inherent characteristic pattern. In the aforementioned detection ofa voice sound, a voiceprint can be obtained as the information inherentto the living body by extracting a vibration as a phase change of theterahertz wave at the site where vocalization vibration can be detected(a bone rising portion) and calculating frequency spectrum for therespective generated sounds. Otherwise a characteristic pattern (apattern inherent to a living body) on a skin surface like a finger printcan be extracted by focusing a terahertz wave on a finger tip, allowingthe focus point to scan successively, detecting slight impression at thefingertip from the phase change at the scanned points, andreconstructing the impression information. Since the positioninformation given by the terahertz wave depends on properties of theliving body, a living body can be identified by this phase change.

The terahertz wave transmitted from the living body gives phaseinformation and amplitude information, both varying with the propertiesof the living body. Therefore, the change of amplitude information, orchanges of amplitude information and phase information from theterahertz wave are utilizable for detection of biological information(information on the living body, or information inherent to the livingbody) For example, in sensing a region of a living body, the differenceof the substances constituting the living body can be observed throughsteps: extraction of the amplitude of the electromagnetic wave asinformation by use of a peak detecting circuit, from electromagneticwave information inputted to biological information-collecting section102; estimation of the quantity of terahertz absorption by the livingbody or the quantity of terahertz reflection by the living body as thebiological information; and comparison of the derived information withthe memorized information. As another example, the living tissue such asprotein constituting the part of the human body can be specified fromthe aforementioned information on the phase change or amplitude changeof the terahertz wave through steps: estimation of characteristics suchas a dielectric constant or impedance of the living body to obtaininformation inherent to the living body; and comparison of the obtainedinformation inherent to the living body with the memorized information.For example, a pattern characteristic to a human body such as a bloodvessel pattern on a retina can be obtained from the difference of abiological tissue constituting the living body. Further, DNA informationcharacteristic to an individual person can be obtained. Information onmovement of a living body can be obtained by monitoring a time-serieschange of material property at a fixed point of the living body (e.g.,pupil contraction caused by local movement of a living body). Other thanthe specification of a living tissue, this method is useful for proof ofthe identified object to be a living body by plotting changes of thedetected quantity for local change of the identification conditions(humidity, temperature, etc.) since the detected quantity depend on thewater content and the temperature conditions.

Several kinds of biological information are mentioned which can bederived from a terahertz wave obtained from electromagneticwave-detecting section 101. However, the information is not limitedthereto. The means for obtaining the biological information is explainedabove by reference to using several circuit constitutions, but theconstitution is not limited thereto. For example, an arithmeticprocessing means may be employed for deriving plural kinds of biologicalinformation without employing a circuit element.

Biological information-memorizing section 103 memorizes referenceinformation corresponding to the biological information obtained bybiological information-collecting section 102. The reference informationon the living body to be identified should be entered preliminarily. Inthe present invention, the entry of the reference information on theliving body into biological information-memorizing section 103 isconducted, for example, by system in which electromagneticwave-detecting section 101 senses a living body to obtain necessarybiological information and this biological information is memorized(106) in biological information-memorizing section 103, but is notlimited thereto. The biological information-memorizing section 103 maybe made detachable from the individual person identification apparatus.Biological information-memorizing section 103, when detached, serves asa key like an ID card, providing a security means for more safe system.With such biological information-memorizing section 103 as a keyfunction, plural individual person identification apparatuses can beused commonly.

Identifying section 104 compares plural kinds of the biologicalinformation from biological information-collecting section 102 with therespective reference information of the living body memorized inbiological information-memorizing section 103, and from the correlation,judges whether the living body to be identified is entered living bodyor not, and outputs the result of the identification. More specifically,in addition to the characteristic pattern inherent to an individualperson, additional biological information (e.g., information on themovement of the living tissue, and information on the material of theliving tissue) is employed to improve the real-time detectableness andprecision of the identification. In the comparison operation, all of thederived plural kinds of information may be utilized, or combination ofthe plural kinds of information may be changed at random in everyidentification operation for higher real-time detectableness and higherprecision of the identification. The change of the combination of thebiological information introduced to the identification apparatus inevery identification operation improves the safety of the system.

The operation of the identification apparatus of the present inventionis described below.

The identification apparatus of the present invention identifies anindividual person through the steps below.

(Entry of Biological Information)

(1) A terahertz wave from a living body is detected.

(2) From the detected terahertz wave, necessary kinds of information areextracted and are memorized in a recording medium.

(Identification)

(1) The memorizing medium having memorized biological information isconnected to the identification apparatus. (This step is omitted whenthe identification apparatus and the memorizing medium are integrated.)

(2) A terahertz wave is detected from the site having biologicalinformation required by the identification apparatus.

(3) From the detected terahertz wave, plural kinds of informationrequired by the identification apparatus are extracted and collected.(Preferably collected are a characteristic pattern inherent to theliving body and biological information for improving the real-timedetectableness of the characteristic pattern.)(4) The respective derived pieces of biological information are comparedwith the reference information memorized in the memory medium, and theliving body is identified by the correlation.

The identification by use of plural kinds of biological information asabove will ensure the real-time detectableness of the identification andwill improve the safety of the system.

EXAMPLES Example 1 Voiceprint Identification

This Example shows an application of an identification apparatus of thepresent invention to identification of an individual person bycombination of plural kinds of organ movement information. A voiceprintidentification apparatus is used in this Example. The voiceprintidentifying apparatus can render unnecessary an ID card or passwordwhich is essential in log-in to an ATM, a personal computer, or thelike.

The voiceprint identification apparatus in this Example has aconstitution as shown in FIG. 1. An impulse wave of a pulse width ofabout 10 psec is employed as the electromagnetic wave. As the biologicalinformation, this Example utilizes vibration 203 of vocal cord 201 ofhuman body 200 and movement 204 of larynx 202 in vocalization as shownin FIGS. 2A and 2B. A person makes a voice by vibrating vocal cord 201.For changing the vocalization state, vocal cord 201 is stretched orshortened by movement of larynx 202 up and down or tilting the larynxforward and backward by muscular tissues around larynx 202 as shown inFIGS. 2A and 2B.

In this example, the terahertz wave projected from electromagneticwave-detecting section 101 is reflected by a portion of larynx 202 backto electromagnetic wave-detecting section 101. The reflected terahertzwave detected by electromagnetic wave-detecting section 101 contains, insuperposition, information on vibration A of voice cord 201 transmittingthrough larynx 202 and information on distance variation caused bymovement B of larynx 202 as a delay time of the terahertz waveintroduced to electromagnetic wave-detecting section 101. By monitoringthe delay time in time series, the distance relation betweenelectromagnetic wave-detecting section 101 and larynx 202 can be derivedaccording to the relation to the electromagnetic wave velocity:Δt=(2Δd)/cwhere Δt: delay time, Δd: positional variation, c: light velocity.

In this Example, the electromagnetic wave-detecting section 101 projectsa terahertz wave to a portion of human larynx 202 at a constant timeinterval. The phase of the terahertz reflected by larynx 202 varies incorrespondence with the position of larynx 202 and the vibration ofvoice cord 201. Biological information-collecting section 102 conductssampling at regular intervals as the terahertz wave projection intervalsof electromagnetic wave-detecting section 101. As described above, thephase of the terahertz is reflected by larynx 202 depends on the stateof larynx 202. Therefore, the delay time Δt of the terahertz wave variesfor each sampling as shown in FIG. 3A (the sampling points being shownby arrows 301). From the dependency of the delay time Δt on the distancebetween electromagnetic wave-detecting section 101 and larynx 202 intime series, a vibration waveform synthesized from vibration A of voicecord 201 by vocalization and movement B of larynx 202 can be detected asshown in FIG. 3B. For this detection, the sampling frequency (i.e., theinterval of terahertz wave projection) should be sufficiently smallerthan vibration A of voice cord 201.

As described above, the vibration waveform derived from the distancerelation between a portion of larynx 202 and electromagneticwave-detecting section 101 is considered to be formed by superpositionof the information on vibration of voice cord 201 caused by vocalizationand the information on movement of larynx 202 for adjusting thevibration state of voice cord 201. Generally the information on thevibration of voice cord 201 and the information on movement of larynx202 for adjusting the vibration state of voice cord 201 are differentgreatly in the frequency characteristics. Therefore, the two kinds ofinformation can readily be separated by filtering or a like arithmeticprocessing. For example, by filtering the above vibration waveform forhuman voice frequency band, a vibration waveform of voice cord 201 canbe derived which varies in vibration frequency in time series as shownin FIG. 3C. Biological information-collecting section 102 converts thetime waveform of vibration A of voice cord 201 as shown in FIG. 3C intoa time-series frequency spectrum as shown in FIG. 3E, and outputs it toidentifying section 104 as voiceprint information on the voice of theperson. On the other hand, the vibration waveform shown in FIG. 3B,which results from synthesis of the voice cord vibration and the larynxmovement, is treated for extraction of the signal component in a lowfrequency region to detect movement of larynx 202 caused by vocalizationof the person as shown in FIG. 3D. This information of movement B oflarynx 202 is also introduced to identifying section 104.

In this Example, as described above, voiceprint information is derivedas a characteristic pattern inherent to a living body, and theinformation on larynx movement in vocalization is also derived from theelectromagnetic information detected by electromagnetic wave-detectingsection 101 for improving the real-time detectableness of voiceprintinformation.

The process of this Example comprises a step of converting the voice ofa person to voiceprint information in time series. Thereby from thevoiceprint information obtained as shown in FIG. 3E, the voice of theperson can be reproduced by converting the voiceprint information tovoice cord vibration information as shown in FIG. 3C.

Identifying section 104 identifies the person by comparing the derivedbiological information with the reference signal memorized in biologicalinformation-memorizing section 103.

In this Example, the voiceprint and larynx movement of a living body areutilized in combination as the plural kinds of biological information,but the combination is not limited thereto. The information for thecombination includes voice information before conversion to thevoiceprint; voice information for a specified keyword; voiceprintinformation for a specified keyword; temperature information, animpedance change, a water content, and a skin thickness around the voicecord; voice tissue information. The number of the kinds of combinedbiological information is not limited to two.

As shown in this Example, combined use of the larynx movementinformation in a voiceprint identification apparatus improves real-timedetectableness in the identification, thereby preventing effectivelypretension to be the subject person, being different from a conventionalmethod such as simple voiceprint recording. This method will improve thesecurity in the identification.

The method of this Example derives voice information of a person fromthe vibration of a voice cord transmitted from a larynx. Therefore, theidentification can be conducted precisely under noisy conditions withoutdetecting an external signal noise component.

Example 2 Fingerprint Identification

This Example shows an application of an identification apparatus of thepresent invention to identification of an individual person by utilizinga combination of personal characteristic pattern with organ movementinformation. A fingerprint identification apparatus is employed in thisExample. The fingerprint identification apparatus can render unnecessarythe ID card or password which is essential in log-in to an ATM, apersonal computer, or the like.

The fingerprint identification apparatus in this Example has aconstitution as shown in FIG. 1. An impulse wave of a pulse width ofabout 10 psec is employed as the electromagnetic wave. The biologicalinformation utilized in this Example is combination of fingerprintpattern on the fingertip and vibration of the pulse transmitted to thefingertip as shown in FIG. 4.

In this example, the terahertz wave is projected from electromagneticwave-detecting section 101 to a fingertip portion of a human body and isreflected to electromagnetic wave-detecting section 101. The projectedterahertz wave is focused on a fine portion in the region of thefingerprint pattern on a fingertip, and focused spot is allowed to scansuccessively the region of the finger print. Incidentally, the method ofscanning of the fingertip is not limited thereto. Otherwise a part orthe entire of the fingerprint region may be collectively scanned withelectromagnetic wave-detecting sections 101 provided in plurality, orthe fingertip is moved for scanning with the focused spot. The reflectedterahertz wave detected by electromagnetic wave-detecting section 101contains information on the shape of the fingerprint pattern A andinformation on the distance of electromagnetic wave-detecting section101 as the delay of time of the electromagnetic wave for reaching theelectromagnetic wave-detecting section 101. Therefore, from the delaytime at the fingertip, the distance relation between electromagneticwave-detecting section 101 and fingertip can be derived according to therelation with the electromagnetic wave velocity:Δt=(2Δd)/cwhere Δt: delay time, Δd: positional variation, c: light velocity.

In this example, electromagnetic wave-detecting section 101 focuses theterahertz wave on the fingertip, allows the focused spot to scan theregion of the fingerprint pattern successively, and outputs the distancerelation between the fingertip and electromagnetic wave-detectingsection 101 at the scanning points to biological information-collectingsection 102. The use of the terahertz wave enables measurement of thedistance between the fingertip and electromagnetic wave-detectingsection 101 with accuracy of micrometers. Therefore, the information onthe delay of the terahertz wave transmitted from electromagneticwave-detecting section 101 to biological information-collecting section102 contains information on the fingerprint impression Further, sincethe surface of the fingertip is vibrated up and down slightly by pulseof the blood vessel, the terahertz wave delay information transmitted tobiological information-collecting section 102 contains information onpulse vibration in addition of the fingerprint impression information.

In this Example, the electromagnetic wave-detecting section 101 projectsa terahertz wave to a fingertip portion of human body 400 at a constanttime interval. The phase of the terahertz reflected from scanning pointson the fingertip varies in correspondence with the fingerprintimpression pattern and vibration of the fingertip by the pulse.Biological information-collecting section 102 conducts sampling at thesame intervals as the terahertz wave projection intervals ofelectromagnetic wave-detecting section 101. As described above, sincethe phase of the terahertz wave reflected by the fingertip depends onthe fingertip impression pattern and the pulse vibration state, thedelay time Δt of the terahertz wave varies for each sampling as shown inFIG. 5A (the sampling points being shown by arrows 501). By obtainingthe relation of the terahertz wave delay Δt with the distance betweenelectromagnetic wave-detecting section 101 and the fingertip in timeseries, synthesized vibration waveform of the fingerprint pattern 401(rise-depression of the fingerprint pattern crossing the scanning lineof the focused terahertz wave) and the vibration waveform of pulse atthe fingertip can be detected as shown in FIG. 5B. The vibrationfrequency of the vibration waveform (signal of the high frequencycomponent in FIG. 5B) corresponding to the fingerprint pattern 401 iscontrolled by scanning frequency with the focused spots of the terahertzwave. The sampling frequency (i.e., the interval of terahertz waveprojection) should be sufficiently smaller than the frequency derivedfrom the impression structure of fingerprint pattern 401 and thescanning frequency for the sensing.

As described above, the synthesized waveform derived from the distancerelation between a scanning point of the terahertz wave on the fingertipand electromagnetic wave-detecting section 101 is considered to besuperposition of the information on fingerprint impression shape and theinformation on the state of the pulse vibration. The signal componentfor the fingerprint impression is controllable by the scanningfrequency, and the vibration component of the pulse in the fingertip isa relatively regular signal component of from tens to hundreds ofhertzes. Therefore, the two kinds of the information are simplyseparable by filtering or a like arithmetic processing. For example, byfiltering the above synthesized waveform for the frequency band of thefingerprint A, information can be obtained, in time series as shown inFIG. 5C, on the changes of the distance (corresponding to theinformation on the distance between the scanning point on the fingertipand the electromagnetic wave-detecting section 101, namely correspondingto the depth of the depression of the fingerprint pattern) and on theinformation on rise-depression of the fingerprint (corresponding to theintervals in the fingerprint pattern). The calculation result isintroduced to identifying section 104. On the other hand, information onpulse vibration in the fingertip can be obtained as shown in FIG. 5D byextracting, from the synthesized waveform obtained from the fingerprintpattern and the pulse vibration as shown in FIG. 5B, the signalcomponent which is periodical and has a lower frequency corresponding tothe pulse vibration transmitted to the fingertip. This information onthe pulse vibration is also inputted to identifying section 104.

Identifying section 104 may conduct a step for reconstructing theinformation on the fingerprint pattern impression arranged in timeseries, corresponding to the scanning route to obtain image informationof the fingerprint pattern.

In this Example, as described above, fingerprint information is derivedas a characteristic pattern inherent to a living body, and for improvingthe real-time detectableness of information of the fingerprint, theinformation on pulse vibration is derived from the electromagneticinformation detected by electromagnetic wave-detecting section 101.

Identifying section 104 identifies the individual person by comparingthe derived biological information with the reference signal memorizedin biological information-memorizing section 103.

In this Example, the fingerprint pattern on the fingertip and pulsevibration transmitted to the fingertip are utilized in combination asthe plural kinds of biological information, but the combination is notlimited thereto. The information for the combination includestemperature at or around the fingertip, an impedance change, a watercontent, and a fingertip tissue. The number of the kinds of combinedbiological information is not limited to two.

The electromagnetic wave employed in the present invention has a certainresolving power, a rectilinear propagation property like light, andpenetrability as the electromagnetic wave. Therefore, the fingerprintidentifying apparatus may be of a noncontact type, being different fromconventional contact type ones.

As shown in this Example, combination of fingertip pulse informationdetection to a fingerprint identification apparatus improves real-timedetectableness in the identification, thereby preventing effectivelypreparation of an imitated fingerprint or direct cutting out of afingerprint for pretension to be the subject person, being differentfrom a conventional method. This method will improve the security inidentification.

The fingerprint identification apparatus is capable of identifying anindividual person without contact with the person, and utilizeselectromagnetic wave which is somewhat penetrative. Therefore, thefingerprint identification apparatus may be housed in a casing. Forexample, an easy-handleable identification apparatus can be producedwhich identifies an individual person automatically without giving astress to the identified object person, for example, by simple touchwith a keyboard or power switch of a personal computer.

Example 3 Retina Identification

This Example shows an application of an identification apparatus of thepresent invention to identification of an individual person bycombination of a personal characteristic pattern with biologicalinformation of the person. A retina identification apparatus is used inthis Example. The retina identification apparatus renders unnecessarythe ID card or password which is essential in log-in to an ATM, apersonal computer, or the like.

The retina identification apparatus of this Example has a constitutionas shown in FIG. 1. An impulse wave of a pulse width of about 10 psec isemployed as the electromagnetic wave. The retina pattern and eye lensshape of a person are utilized as the biological information in thisExample as shown in FIG. 6. FIG. 6 contains a sectional view and a frontview of a human eyeball. In FIG. 6, retina 601 is an inside wall of theeyeball, functioning like a film of a camera. In this Example, the terma “retina pattern” signifies a pattern of a blood vessel on retina 601.Eye lens 602 functions like a lens of a camera and adjusts the focus byadjusting the thickness of eye lens 602. Iris 603 has a hole called apupil 604 at the center. Iris 603 and pupil 604 function like anaperture of a camera and adjust the quantity of light entering the eye.Iris 603 has a pattern (generally called an iris pattern) characteristicto an individual person, being utilized frequently for identification ofthe person.

In this Example, the terahertz wave projected from electromagneticwave-detecting section 101 is introduced through eye lens 602 to retina601, reflected by this retina 601 back to electromagnetic wave-detectingsection 101. In this process the terahertz wave projected fromelectromagnetic wave-detecting section 101 is focused on a fine spot inthe region of the retina pattern on retina 601, and the focused spot isallowed to scan the region successively. The method for scanning theretina 601 is not limited to the above method. Otherwise the scanningmay be conducted by use of plural electromagnetic wave-detectingsections for collective scanning of a part of retina 601 or the entireregion of the retina pattern, or may be conducted by moving the eyeball.The reflected terahertz wave detected by electromagnetic wave-detectingsection 101 contains information on a retina pattern obtained fromdifference of a blood vessel pattern on retina 601 from other livingtissues, and additional information in superposition on terahertz waveabsorption/reflection characteristics obtained from the thickness shapeB of the eye lens existing in the transmission route of the terahertzwave as variation of the terahertz wave reaching electromagneticwave-detecting section 101.

In this Example, electromagnetic wave-detecting section 101 focuses theterahertz wave on retina 601; allows the focused spot to scan the regionof retina pattern A successively to measure absorption/reflectioncharacteristics of the terahertz wave at the scanned spots; and outputsthe measurement results to biological information-collecting section102. The terahertz wave covers various absorption wavelengths of livingtissues, having different transmission characteristics for therespective living tissues. Therefore, the information on the bloodvessel pattern (retina pattern) on retina 601 can be obtained bydetecting the difference in the transmission characteristics. Further,in the terahertz wave transmission path, eye lens 602, for Example,exists. Naturally, the eye lens 602 affects the transmissioncharacteristics of the terahertz. The eye lens 602 incessantly changesits thickness for focusing. This thickness change is considered tochange incessantly the terahertz wave transmission path in eye lens 602.Therefore, the intensity information of the terahertz introduced tobiological information-collecting section 102 contains also theintensity change information caused by the thickness change of eye lens602 in addition to the information on the living tissue of retina 602.

In this Example, electromagnetic wave-detecting section 101 projects aterahertz wave onto retina 602. The intensity of the reflected terahertzwave from the scanning spot on retina 601 is changed by the differencein the living tissues (difference between the blood vessel pattern andother living tissue) in the retina pattern, and transmission path lengthof the terahertz wave caused by the thickness change of eye lens 602.Biological information-collecting section 102 detects the response ofthese terahertz waves in time series to obtain a synthesized oscillationwaveform which is composed of a vibration waveform of the retina patterncorresponding to difference in the living tissue of the retina (theshape of the retina pattern on the scanning line of the focusedterahertz wave) and a response waveform corresponding to the shape ofeye lens 602 as shown in FIG. 7A. The frequency of the obtained responsewaveform corresponding to the retina pattern (signal of high frequencycomponent in FIG. 7A) is controlled by the scanning frequency of thescanning spot by the focused terahertz wave.

As described above, the synthesized waveform obtained from the change oftransmission state caused by the living tissue in the transmission pathof the terahertz wave is considered to be formed by superposition of theinformation on the retina pattern on retina 601 and the information onthe thickness shape of eye lens 602. The signal component correspondingto the retina pattern is controllable by the scanning frequency, and thesignal component corresponding to the thickness change of focusing ofeye lens 602 is readily separable by arithmetic processing likefiltering since this component distributes in a low frequency region.For Example, by filtering this synthesized waveform for the frequencyregion of the retina pattern, a signal can be obtained which shows thechange of the intensity (corresponding to the difference between theliving tissues on retina 601) and of the frequency (corresponding tointervals of the retina) in time series as shown in FIG. 7B. Thiscalculation result is outputted to identifying section 104. On the otherhand, a signal component corresponding to the thickness shape of eyelens 602 as shown in FIG. 7C is obtained by extracting the signalcomponent in the low frequency region from the synthesized waveformshown in FIG. 7A. This calculation result is also outputted toidentifying section 104. In this Example, a larger thickness of the eyelens gives a smaller signal intensity of the obtained electromagneticwave. However, with a certain signal processing method, a smallerthickness of the eye lens gives a smaller signal intensity of theobtained electromagnetic wave.

Identifying section 104 may contain a step of reconstructing thetime-series information of the retina pattern according to the scanningroute to obtain information on the image of the retina pattern.

The focusing point of the eye can be changed by changing the position ofelectromagnetic wave-detecting section 101 relative to the eyeball. Thefocusing point of the eye caused change of the shape of the eye lens,more specifically change of thickness of the eye lens. The informationon this movement for the shape change can be outputted as the biologicalinformation to identifying section 104.

As described above in this Example, retina information is obtained as acharacteristic pattern inherent to a living body, and for improvement ofreal-time detectableness of the retina information, information on theshape of the eyeball or on movement for changing shape B of the eyeballis obtained from electromagnetic wave information detected byelectromagnetic wave-detecting section 101.

Identifying section 104 compares the biological information with areference signal of living body memorized in biologicalinformation-memorizing section 103 to identify the individual personfrom the relation between the information and the reference signal.

As the plural kinds of biological information, a retina pattern of aneyeball, and a shape of an eye lens or movement for shape change of theeye lens are utilized in combination in this Example. However, thecombination is not limited thereto. For example, the information to becombined includes information on an iris; contraction or dilation of apupil; temperature information, impedance change, water content aroundan eyeball; movement of an eyeball itself. The number of the kinds ofcombined biological information is not limited to two.

As shown in this Example, combined use of the eye lens information inretina identification improves real-time detectableness in theidentification, thereby preventing effectively pretension to be thesubject person by collection and imitating a retina pattern, or directcutting-out of the pattern. This method will improve the security inidentification.

The electromagnetic wave used for detection of a retina pattern is lessstimulative to the eye than light, and the identification be conductedwithout damaging the living tissue of the eyeball by abrupt irradiationof high-power light. Thus the present invention provides anidentification apparatus highly safe to the human body.

This application claims priority from Japanese Patent Application No.2004-092398 filed on Mar. 26, 2004, which is hereby incorporated byreference herein.

1. A method of identification of a living body, comprising the steps of:a first detecting step of detecting a first electromagnetic wave in afrequency band ranging from 300 GHz to 30 THz reflected from the livingbody; a second detecting step of detecting a second electromagnetic wavein the frequency band reflected from the living body, wherein the firstand second electromagnetic waves include superposed biologicalinformation; a deriving step of deriving a time waveform by using thefirst and second electromagnetic waves; an extracting step of extractingthe biological information by filtering the time waveform through afrequency property; and a comparing step of comparing the biologicalinformation with preliminarily memorized biological information, whereinthe biological information extracted from the time waveform is derivedfrom delay times of the first and second electromagnetic waves caused bya change of position in time of a portion of the living body.
 2. Themethod of identification according to claim 1, wherein the biologicalinformation is information on positional variation selected from thegroup consisting of pulse vibration, voice cord variation, bonevibration, shape change of eye lens, pupil contraction and pupildilation.
 3. The method of identification according to claim 1, whereinthe biological information is any one selected from the group consistingof a fingerprint, a voiceprint and a retina pattern.
 4. A method ofidentification of a living body, comprising the steps of: a firstgenerating step of generating a first electromagnetic wave pulse in afrequency band ranging from 300 GHz to 30 THz; a first detecting step ofdetecting the first electromagnetic wave pulse reflected by the livingbody; a second generating step of generating a second electromagneticwave pulse in the frequency band; a second detecting step of detectingthe second electromagnetic wave pulse reflected from the living body,wherein the first and second electromagnetic wave pulses includesuperposed biological information; a deriving step of deriving a timewaveform by using the first and second electromagnetic wave pulses; anextracting step of extracting the biological information by filteringthe time waveform through a frequency property; and a comparing step ofcomparing the biological information with preliminarily memorizedbiological information, wherein the biological information extractedfrom the time waveform is derived from delay times of the first andsecond electromagnetic wave pulses caused by a change of position intime of a portion of the living body.
 5. An apparatus for identifying aliving body, comprising: a detecting section for detecting first andsecond electromagnetic wave pulses in a frequency band ranging from 300GHz to 30 THz reflected from the living body, the first and secondelectromagnetic wave pulses including superposed biological information;an information-collecting section for deriving a time waveform by usingthe first and second electromagnetic wave pulses and extracting thebiological information by filtering the time waveform through afrequency property, a memory section for preliminarily memorizingbiological information; and an identifying section for comparing thebiological information extracted by the information-collecting sectionwith the biological information memorized by the memory section, whereinthe biological information extracted from the time waveform is derivedfrom delay times of the first and second electromagnetic waves caused bya change of position in time of a portion of the living body.
 6. Anapparatus for identifying a living body, comprising: a generatingsection for generating first and second electromagnetic wave pulses in afrequency band ranging from 300 GHz to 30 THz; a detecting section fordetecting the first and second electromagnetic wave pulses reflected bya living body, the first and second electromagnetic wave pulsesincluding superposed biological information; an information-collectingsection for deriving a time waveform by using the first and secondelectromagnetic wave pulses and extracting the biological information byfiltering the time waveform through a frequency property; a memorysection for preliminarily memorizing biological information; and anidentifying section for comparing the biological information extractedby the information-collecting section with the biological informationmemorized by the memory section, wherein the biological informationextracted from the time waveform is derived from delay times of theelectromagnetic wave caused by a change of position in time of a portionof the living body.
 7. The apparatus according to claim 6, wherein theinformation-collecting section derives the time waveform regarding thebiological information, the memory section preliminarily memorizes atime waveform regarding the living body, and the identifying sectioncompares the time waveform regarding the living body derived by theinformation-collecting section with the time waveform regarding theliving body memorized by the memory section to identify the living body.8. A method of identification of a living body, comprising the steps of:a first generating step of generating a first electromagnetic wave pulsein a frequency band ranging from 300 GHz to 30 THz; a first detectingstep of detecting the first electromagnetic wave pulse reflected by theliving body; a second generating step of generating a secondelectromagnetic wave pulse in the frequency band; a second detectingstep of detecting the second electromagnetic wave pulse reflected fromthe living body, wherein the first and second electromagnetic wavepulses include superposed biological information; a deriving step ofderiving a time waveform by using the first and second electromagneticwave pulses; a separating step of separating a time waveform regardingthe biological information by filtering the time waveform through afrequency property; and a comparing step of comparing the derived timewaveform regarding the biological information with a time waveformregarding preliminarily memorized biological information, wherein thebiological information extracted from the time waveform is derived fromdelay times of the first and second electromagnetic wave pulses causedby a change of position in time of a portion of the living body.
 9. Themethod of identification according to claim 8, further comprising a stepof identifying the living body by the result of the comparing step. 10.A method for deriving a time waveform, comprising the steps of:detecting an electromagnetic wave in a frequency band ranging from 300GHz to 30 THz reflected from the living body, the electromagnetic waveincluding superposed biological information; and deriving a timewaveform of the electromagnetic wave by sampling the electromagneticwave detected in the detecting step, wherein the biological informationextracted from the time waveform is derived from a delay time of theelectromagnetic wave caused by a change of position in time of a portionof the living body.
 11. The method of identification according to claim1, further comprising a step of identifying the living body by theresult of the comparing step.